Inertia impact firing mechanism for munitions having retarding means



May 12,1970 E. BOWERS 3,511,134

- INERTIA IMPACT FIRING MECHANISM FOR MUNITIONS HAVING RETARDING MEANS Filed April 8, 1968 IN VENTOR.

K RUSSELL E. BOWERS E .i BY W ATTORNEY.

UhitedStates Patent 3,511,184 INERTIA IMPACT FIRING MECHANISM FOR MUNITIONS HAVING RETARDING MEANS Russell E; Bowers, Richmond, Ind., assignor to Avco Corporation, Richmond, Ind., a corporation of Delaware I Filed Apr. 8, 1968, Ser. No. 719,417 Int. Cl. F42c 1/04, 1/06, 15/24 ABSTRACT OF THE DISCLOSURE manner at impact angles from 0 to 85 from the vertical.

The invention includes timing means for insuring that the firing will not detonate the explosive charge in response to forces of deceleration less than those developed upon impact upon the target.

The invention relates to impact firing mechanisms and is particularly concerned with such mechanisms for use with retarded bombs which are launched from aircraft attlow levels and retarded by drag fins which open immediately after launch and create a sudden deceleration which may optionally be utilized to trigger the operation of a fuze. -Where these forces are so utilized the fuze is set to respond thereto in manner which will detonate the explosive charge within a predetermined time after launch. In othercircumstances it is desirable to set the fuze so it will not be affected by the deceleration caused by the drag fins but to set the fuze to operate to detonate the explosive device upon impact with the target.

Prior art inertia impact devices have relied on mechanisms containing mass actuators in the form of generally rectangular weights which slide forwardly on impact. If impact is not normal or nearly normal to the line of flight ofthe bomb, the necessary deceleration forces are sometimesnot reached to stab the detonator, their movement being slowed up by substantial sliding friction against the sides of the enclosure in which they are located.

In the use of retarded bombs utilizing such prior art mechanisms a timer mechanism is provided which is triggered immediately upon the exertion of the initial high value deceleration forces developed when the drag fins open. In such cases it is desirable to provide an impact fuze which will not only insure the detonation of the explosive charge on impact should the timer mechanism become ineffective, but will also insure detonation if the timer mechanism is purposely set to become ineffective.

A principal object of the invention is to provide an impact firing mechanism which will be positive at angles of impactvarying widely from 0".

Another object of the invention is to provide an impact firing mechanism which will be positive at angles of drag-induced deceleration but will function upon impact-induced deceleration.

Other objects and advantages of the invention will more clearly appear when reference is had to the accompanying drawings, in which:

FIG. 1 is a schematic viewof an impact firing mechanism constructed according to the principles of the invention with the mechanism in initial position, prior to actuation by any forces of deceleration; v

FIG. 2 is a similar view of the mechanism in the position assumed when firing occurs; and

3,511,184 Patented May 12, 1970 "ice FIG. 3 is a side elevational view with parts in section of a fuze assembly incorporating the mechanism of FIGS. 1 and 2 showing the latter when actuated by high value deceleration forces but with the fuze oriented to nonfiring position until such forces are relieved.

Referring first to FIG. 3, the novel impact firing mechanism, generally designated as 10, is mounted within a frame 11 secured to the inner bomb casing. In frame 11 is likewise mounted a timing device 12 which releases an arm 13 at the termination of its cycle so that detonator holder 14 can rotate around an axis 15 to align the firing pin 20 with the detonator 16 contained in a cavity in detonator holder 14. This position is shown in FIG. 2. The relief hole or safing cavity 19 shown in FIG. 3 is aligned with the pin 20 during the time the arm 13 is extended to prevent the rotation of holder 14 on its axis, but the pin 20 is aligned with detonator 16 when the holder 14 is rotated to armed position at such time as the forces of deceleration are relieved. The cooperation of these parts will hereinafter more clearly appear.

The casing in which frame 11 is mounted is provided with extensible drag fins, operative to spring outwardly when the bomb body is launched and thereby to decelerate the bomb as high value deceleration forces are produced. This construction is well understood in the art and is not, in and of itself, a part of the present invention and will not be described in detail.

It will be understood that the direction of bomb flight is indicated by the arrows A in the various figures and the forces of deceleration which are effective on the assembly when the drag fins are operative, are in the opposite direction.

The impact firing mechanism of the invention comprises inertia ball member 21 rotatably mounted in a cylindrical race 22 with sufficient clearance to permit it easily to slide lengthwise of the race. The race is formed as a cylinder having an interior bore and a fixed stop 23 at one end. A movable head or piston is integrally secured to a rod 20 which terminates in a firing pin. This rod slides in a guideway formed at the end of the cylinder opposite the stop 23. The head 24 is normally maintained in the position shown in FIG. 1 by spring 25 of sufiicient strength to hold the ball against movement under the influence of forces of a magnitude of approximately ten times the force of gravity. The spring is compressed into the position shown in FIG. 3 when deceleration forces of this magnitude, operating on the body of the bomb, act upon the mass of the ball 21 and its inertia causes it to move in the direction indicated by the arrows A. Rod 20 is suitably mounted for free sliding movement through a central aperture in race 22.

Coming now to the operation of the impact firing device under different conditions, it will be understood that its initial position is as shown in FIG. 1 with the ball forced back against stop 23 by the force of spring 25. In normal operation for tactical use on retarded bombs, the initial retardation effected by the retarding fins will cause the ball mass to move forward toward firing position but the timer will have been set so that at this time it will not have caused the withdrawal of arm 13 from detonator holder 14 and the latter will not have been allowed to rotate on its axis 15. Accordingly, the detonator 16 will have been maintained in a safe or out-of-line position with the firing pin which under these conditions can only enter the relief hole 19 as shown in FIG. 3.

However, when the retarding forces are relieved the firing pin spring 25 will force the ball 21 to return to its original position and the impact firing mechanism 10 will then be in position for the fuze to arm in its normal manner, namely by the timer completing its cycle, withdrawing arm 13 and rotating detonator holder 14 on its 3 axis 15 until the detonator 16 is aligned with the firing pin. Under these conditions (see FIG. 2) the firing pin is forced into the detonator when the ball mass senses final impact deceleration thereby initiating the action of the detonator.

According to the invention the ball, confined relatively loosely within its race, rolls freely in the desired direction upon impact, thereby reducing the friction inherent in impact firing mechanisms in which rectangular weights slide toward the firing pin. With this construction I obtain much greater impact sensitivity. I have found that effective firing is accomplished even if the bomb falls on target at angles as high as 85 from the verticala condition which often results in the failure of prior art impact devices to fire.

It is important also to note that in accordance With the invention the combined mechanism permits a bomb to fall free if used in free-drop bombs with no initial movement being experienced by the impact firing mech anism, while at the same time the bomb may be used with retarded bomb equipment with ineffective movement of. the impact mechanism during the time the initial retardation forces produced by the drag fins take place, but with the ball resuming its proper position for insuring positive stabbing of the detonator on impact after these forces have been relieved.

The mechanism by which the detonator holder 14 is rotated on its aXis 15 from ineffective position to firing position is well known in the art and will not be described herein.

Having described my invention, I claim:

1. In a fuze of the type adapted to be installed in a munition which incorporates retarding means and fires on impact, the combination of:

a detonator carrier formed with a detonator-holding cavity and a safing cavity and adapted to be displaced from a safe position to an armed position, at which the detonator-holding cavity is in alignment with a firing train;

means including a timer for restraining displacement of the detonator carrier from the safe position to the armed position until the expiration of a predetermined time following the release of said munition for flight;

a firing member comprising a piston portion and a piston rod portion terminating in a firing pin, said 4 firing pin and rod portion being in axial alignment with said safing cavity when said detonator carrier ,1 is in the safe position;

a cylindrical housing formed to define an interior bore for the piston portion and a guideway for the piston rod portion;

an inertia ball member contained within said housing in position to exert thrust on said piston portion;

and spring means for thrusting said piston portion inwardly of said housing so that, in the absence of a deceleration forces said firing pin is out of said safing cavity and exerts no restraint on said detonator carrier;

said inertia ball member responding to the deceleration forces developed by the retarding means to overcome the force of the spring means and to project said firing pin into said safing cavity whereby said firing pin functions to prevent arming of the fuze when retarding forces sufficient to overcome the force of said spring are present during flight of said munition,

said spring forcing the inertia ball member and piston V inwardly of said housing, upon the cessation of said forces, thereby to permit the detonator carrier to be displaced to the armed position at which the detonator holding cavity is aligned with the firing P the inertia ball member being responsive to impact forces to exert a thrust against the piston portion which overcomes the force of the spring and stabs the firing pin into said detonator holding cavity.

References Cited UNITED STATES PATENTS 1,310,350 7/1919 Kennedy.

2,044,819 6/1936 Taylor 1024 2,834,292 5/1958 Viasmensky 10279 3,286,634 11/1966 Weber 10278 X 3,316,841 5/1967 McFann et a1 102-4 3,351,017 11/1967 Myers 10276 BENJAMIN A. BORCHELT, Primary Examiner C. T. JORDAN, Assistant Examiner US. Cl. X.R. 102-73 m3? UNITED STATES PA'IIQNI OFFICE CERTIFICATE OF CORRECTION 3,511,184 Dated Patent No.

Inventor(s) Russell E. Bowers It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 1, line 61,

Delete "pact firing mechanism which will be positive at angles of" and insert pact mechanism which will not function as a result of (SEAL) Atteat:

WILLIAM E. Barnum, JR. Edward M. Fletchu-Jr. Gamissioner of Patents 

